Induction heating device with a controlled feeding mechanism

ABSTRACT

In an induction heating device including an oscillator with a high frequency output circuit, a multiple turn induction heating coil with an internal workpiece-receiving passageway connected in the output circuit, means for sequentially feeding workpieces through the passageway and control means for actuating the feeding means, there is provided an energizable means for actuating the control means only when high frequency current is flowing in the output circuit of the oscillator whereby the feeding means is operable only when heating current is flowing in the coil.

United States Patent [72] Inventor Edmund N. Curcio South Orange, NJ.[21] Appl. No. 875,638 [22] Filed Nov. 12, 1969 [45] Patented Aug. 24,1971 [73] Assignee Park-Ohio Industries, Inc.

Cleveland, Ohio [54] INDUCTION HEATING DEVICE WITH A CONTROLLED FEEDINGMECHANISM 2 Claims, 1 Drawing Fig.

[52] U.S.C1 219/10.69, 219/1075, 219/10.55,219/10.77 [51] Int. Cl H05b5/00, HOSb 9/06 [50] Field of Search 250/265, 214, 207; 219/10.69, 10.55

[56] References Cited UNITED STATES PATENTS 2,329,188 9/1943 Denneen eta1 2l9/l0.69X

2,404,147 7/1946 Strickland, Jr. 219/10.77 X 2,993,973 7/1961 Johnson eta1 219/1055 3,181,030 4/1965 Weinstein 250/207 X 3,281,567 10/1966Meissner et al.. 219/1077 X 3,316,380 4/1967 Pansing 219/1055 3,412,22711/1968 Anderson 219/1055 Primary Examiner-J. V. Truhe AssistantExaminer-L. H. Bender Au0rneyMeyer, Tilberry and Body PATENIEMpemn i3.601, 571

I NVEN TOR. EDMUND N. CURCIO ATTORNEYS INDUCTION HEATING DEVICE WITH ACONTROLLED FEEDING MECHANISM The present invention relates to the art ofinduction heating and more particularly to an induction heating devicehaving a controlled feeding mechanism.

The invention is particularly applicable in controlling the sequentialfeeding of elongated, cylindrical workpieces through a multiturninduction heating coil, and it will be described with particularreference thereto; however, it should be appreciated that the inventionhas much broader applications and may be used for feeding variousworkpieces through such a multiturn induction heating coil.

It is somewhat standard practice to harden workpieces, such as bolts andnuts, by passing them through the central workpiece-receiving passagewayof a multiturn induction heating coil connected in the output circuit ofa power oscillator. While passing through the coil, these workpieces areheated to the appropriate hardening temperature so that they may besubsequently quench-hardened. In the past, the device, or mechanism, forfeeding the workpiece through the coil was turned on when power wasconnected to the oscillator. The feeding mechanism continued to operateand feed workpieces through the coil until manually stopped. Thisarrangement caused certain difficulties. It was noted that certain boltsand nuts were not properly hardened by such an installation. Since theparts were generally in large volumes, it was difficult, if notimpossible, to separate the unhardened workpieces from the hardenedworkpieces. Consequently, the location of any insufficiently hardenedpieces required a complete rerun of the whole batch. This was timeconsuming and expensive.

The present invention is directed toward an induction heating mechanismwith a controlled feeding device which overcomes the difficultiespreviously encountered with the arrangement discussed above. Inaccordance with the present invention, there is provided a sensing meansresponsive to the presence of a high frequency field in the outputcircuit of the oscillator. This sensing means is used to control thefeeding device so that the feeding device is not operative when theoutput circuit of the oscillator is not conducting current. By usingthis invention, it is assured that all workpieces are properly heatedbefore being quenched. Consequently, the probability of unhardenedworkpieces being found in a batch of workpieces is substantiallydiminished, if not completely eliminated.

The primary object of the present invention is the provision of aninduction heating device for heating a series of workpieces by theoutput circuit of an oscillator, which device includes means for feedingthe workpieces only when the output circuit of the oscillator isoperating.

Another object of the present invention is the provision of an inductionheating device for heating a series of workpieces by the output circuitof an oscillator, which device includes means for feeding the workpiecesonly when the output circuit is operating and which device may beincorporated into existing induction heating equipment.

Yet another object of the present invention is the provision of aninduction heating device for heating a series of workpieces by theoutput circuit of an oscillator, which device includes a fluorescenttube for sending current flow in the output circuit of the oscillatorand for controlling the feeding of parts accordingly.

These and other objects and advantages will become apparent from thefollowing description used to illustrate the preferred embodiment of theinvention as read in connection with the accompanying drawing in which:

The single FIG. is a schematic diagram showing the preferred embodimentof the invention.

Referring now to the drawing, wherein the showings are for the purposeof illustrating a preferred embodiment of the invention only, and notfor the purpose of limiting same, the sole figure shows a feedingmechanism A for feeding a plurality of workpieces B into a heating andquench-hardening device.

This device includes an oscillator C for powering a multiturn inductionheating coil D having an internal workpiece-receiving passageway 10. Thefeeding mechanism A is started by circuit E controlled, in turn, by acontrol device F, which forms the essential part of the presentinvention.

Referring now to the feeding mechanism A, this device is onlyschematically represented in the drawing and various changes can be madewithout departing from the intended spirit and scope of the presentinvention. Also, only essential elements are schematically representedas that is suff cient to define the present invention. Mechanism Aincludes rails 20 extending through passageway 10, an inclined ramp 22down which the workpieces are passed in sequence from a hopper 24. It isappreciated that bulk feeding can be accomplished in variousarrangements and that the workpieces B,-in some instances, need not beoriented as illustrated. In accordance with the illustrated embodimentof the invention, an escapement 30 having an electrically indexedescapernent wheel 32, controlled by line 34 and ground 36 electricallyconnected to control device or timer 40, is used to introduce theworkpieces onto the rails 20, only one of which is shown. Although thisarrangement feeds only one workpiece at a time, other escapements couldbe used for feeding'more than one workpiece, especially when randomorientation is dictated by the particular shape of the workpieces beingheated. A cylinder 50 having a push rod 52 terminating in an outwardlyextending nose 54 periodically moves toward the coil D for forcing theworkpieces through the coil wherein they are inductively heated. Inaccordance with the illustrated embodiment, the cylinder 50 iscontrolled by pneumatic lines 60, 62 by a valve 64 having an air inletsupply 66 and an air outlet exhaust or sump 68. Valve 64 is, in turn,electrically controlled by lines 70, 72 and ground connection '74 fromthe sequence timer 40.

- In operation of the device so far explained, timer 40 indexesescapement 30 to drop the workpiece onto the rails 20 after which thepush rod 52 pushes the workpiece into the coil and then the push rod isretracted. When an additional workpiece enters the coil, a heaterworkpiece is forced from the coil as it is dropped into the quench tank76 where it is quenchhardened and then removed for subsequent use. Afterthis operation has taken place, the timer or control device 40 actuatesthe escapement to place another workpiece onto rails 20. Repeatedoperation of the escapement 30 and the push rod 52 in timed relationshipby control device or timer 40 successively feeds the workpiece throughthe induction heating coil. The cross section of passageway it) matchesthe workpieces in a manner which provides optimum induction heatingduring passage of the workpieces through the coil.

Referring now to the oscillator C, this oscillator is also schematicallyillustrated and various changes could be made without departing from theintended spirit and scope of the present invention. As illustrated, theoscillator includes a plate 82, a cathode 84, and a grid 86. The gridincorporates any appropriate circuitry, illustrated by box 88, forproviding oscillations. This aspect does not form a part of the presentinvention. Input circuit includes various other circuitry and componentswhich are not essential to understand the present in vention',therefore, for simplicity they have been eliminated. Suffice it to say,that a three phase power from lines a, b, and 0 provides the input powerfor the input circuit 90 which drives the oscillator. The output circuit97. of the oscillator includes standard capacitors 94, 96 and inductor98 that cause proper oscillation of the output circuit when connectedwith the induction heating coil located across output leads 100, 102.The operation of the oscillator is well known in the induction heatingart and no further discussion is deemed necessary.

In accordance with known practice, the induction heating coil D employsan encapsulating casing and multiple turns 112, which are water cooledwith internal passages. The passageway 10 through the coil has a shapeto match the desired heating effect and the coil surrounds thepassageway to provide efficient coupling with the workpieces as they aremoving through the passageway.

The feeding mechanism A is started by a circuit including lines 120, 122connected with an AC source L L A start button, or switch, 124 energizesthe timer 40 and, also, a normally open holding switch 126 through aholding coil 128. As the switch 124 is depressed, the holding switch 126is closed to start the feeding mechanism. To stop the feeding mechanism,normally closed switch 129 is opened to open switch 126. Of course, thisstarting circuit is only schematic in nature and various otherarrangements could be used for energizing the feeding mechanism.

Referring again to the oscillator C, the control device F for thefeeding mechanism is illustrated as a sensing element 130 including astandard fluorescent tube 132 mounted within the field created by RFcurrent in circuit 92 by a mounting element 134. In accordance with theinvention, a sensing element 130 involves a device for sensing thepresence of current flow within the output circuit 92 of the oscillatorC. It has been found that a fluorescent tube can be used for thispurpose if the tube is positioned in close proximity to the outputcircuit. Generally the output current is a RF current which causes thecoating of the fluorescent tube to glow. This creates a light sourcewhen RF current is flowing in circuit 92. Mounted adjacent to thefluorescent tube is a photo-responsive tube 146 which is actuated, ormade conductive, when the coating of the fluorescent tube 132 starts toglow in response to the presence of high frequency current within theoutput circuit of the oscillator. in accordance with the invention, thesensing element 130 blocks the operation of the control device 40 at anytime when high frequency is not flowing in the output circuit 92. Toaccomplish this objective, an illustrated circuit is frequency withinthe output circuit 92, the coating of the fluorescent light stopsglowing. This renders the tube 136 nonshown wherein coil 138 connectedacross lines L L controls normally open switch 140. it is appreciatedthat other currentsensing elements of the type which create a signal,preferably a light signal, when current flows in circuit 92. The circuitactuated by the sensing device must be modified to be responsive to theparticular current-sensing element being employed.

In operation, when the oscillator is generating a high frequency withincircuit 92, the coating of the fluorescent tube 132 glows to create alight source. This light source renders the photo-responsive tube 136conductive which actuates coil 138. This closes switch 140 so that thefeeding mechanism may be operated, as previously explained, by controldevice or timer 40. As so far explained, the feeding mechanism could notbe operated until the oscillator C is in a condition for heating theworkpieces. If for any reason the oscillator discontinues heating bydiscontinuing the high conductive which opens switch 140. The feedingdevice is therefore immediately shut off. Consequently, no workpiecescan be discharged into the quench tank and into subsequent supplied ofworkpieces without being properly heated and quench-hardened.

As a slight modification, the starting circuit F could be changed tohave continuous operation so that the switch would successively actuateor deactuate the control means 40 without requiring the attention of theoperator for restarting the feeding mechanism. The present invention, asillustrated, prevents actuation of the feeding mechanism until theoscillator is functioning properly and requires attention of theoperator when the oscillator, for any reason, stops oscillating. Thisbrings the operator'to the installation so that he may remove theworkpieces within the coil and place them back into the hopper so thatimproperly heated workpieces will not be fed into the quench tank by acircumstance wherein the oscillator stops oscillating and then startsoscillating for some reason. In

this circumstance, certain workpieces within the passageway' 10 could becooled before quenching which could produce an improperly hardenedworkpiece. For this reason, the illustrated embodiment of the presentinvention wherein the feeding device is completely deactuated andrequires operator attention before starting up again is preferred.

Having thus defined my invention, I claim: 1. In an induction heatingdevice comprising an oscillator with a high frequency output circuit, amultiple turn induction heating coil with an internalworkpiece-receiving passageway connected in said output circuit, meansfor feeding workpieces through said passageway, and control means foractivating said feeding means, the improvement comprising: energizablemeans for activating said control means of said feed means only whensaid control means is in a selected condition, and a light sourceresponsive to high frequency current flow in said output circuit of saidoscillator for causing said energizable means to be in said conditiononly when said current flow is present in said output circuit.

2. The improvement as defined in claim 1 wherein said energizable meansincludes a circuit with a light-responsive element, a power source, aswitch-actuating electrical component and a switch means for operatingsaid control means when said switch means is actuated and saidlight-responsive element being positioned adjacent said light source foractuation thereby so that said switch means is activated.

1. In an induction heating device comprising an oscillator with a highfrequency output circuit, a multiple turn induction heating coil with aninternal workpiece-receiving passageway connected in said outputcircuit, means for feeding workpieces through said passageway, andcontrol means for activating said feeding means, the improvementcomprising: energizable means for activating said control means of saidfeed means only when said control means is in a selected condition, anda light source responsive to high frequency current flow in said outputcircuit of said oscillator for causing said energizable means to be insaid condition only when said current flow is present in said outputcircuit.
 2. The improvement as defined in claim 1 wherein saidenergizable means includes a circuit with a light-responsive element, apower source, a switch-actuating electrical component and a switch meansfor operating said control means when said switch means is actuated andsaid light-responsive element being positioned adjacent said lightsource for actuation thereby so that said switch means is activated.